Changing Service Contract items status

I am looking for a way to do mass change of statuses of Service contract items. Please guide me. Here is my requirement.

I have a service contract with lots of line items. I need to change the statuses of all items in one go by selecting all.

I have looked at options available in change process functionality of service contract, but unfortunately it looks like not going to fulfil my requirements i may be missing something. Not sure if i could achieve by implementing BAdI